The present invention relates to thermally actuated valves, or thermostats as they are often referred to, employed in the coolant passages of liquid cooled internal combustion engines for controlling flow of the engine coolant. Typically such thermostats are employed in the water outlet of the cooling passages in an engine cylinder head for controlling flow of coolant to the vehicle radiator.
In marine engine applications, the engine coolant is often sea water taken in by the water pump through a sea cock or inlet port provided below the waterline of the craft in which the engine is employed. Marine engine applications are typically of the open circuit coolant arrangement wherein the coolant is not recirculated through the engine but is discharged in a return port to the sea. In marine engine applications problems have arisen in providing thermostats for controlling the flow of sea water to maintain the desired engine temperature where sea weed and other flotsum have lodged in the thermostat valve seat and poppet and caused the thermostat to malfunction.
In engine applications where failure of the thermal actuator to open the poppet valve would result in rapid overheating and failure of the engine, particularly in heavy duty engine applications such as truck or marine service it has been desired to provide a coolant overpressure relief function to the thermostat. As the temperature in the engine coolant passages rises above the boiling point of the coolant, it is desired to have the pressure of the water vapor acting over the surface area of the poppet cause the poppet to open and permit circulation of coolant through the engine.
In order to provide effective sealing of the thermostat poppet against its seat in the closed position for providing fast warmup and sealing of the mounting of the thermostat in the engine coolant passage to prevent leakage around the thermostat, it has been desired to provide a resilient material for sealing about the valve seat and the mounting flange of the thermostat. It has further been desired to provide a low cost readily manufacturable engine thermostat providing the above-described features in a structure which provides repeatability, reliability and long life in severe engine application such as truck and marine engines.